Decelerometer



March I, 1938.

P. w. CALHOUN I 2,109,523

DECELEROMETER Filed Oct. 14, 19:6

I gvwcm 1. lZUaZ/wm anon/wen.

Patented Mar. 1, 19 38 UNITED STATES PATENT OFFICE.

DECELEROMETEB. Paul White Calhoun, Madison, Fla.

Application 2 Claims.

Broadly considered, this invention aims to provide a means whereby, through the instrumentality of a pendulum normally held in an upstanding position, but capable of being dislodged from that position when the brakes of a car are applied, the checking power of the brakes may be determined. Another object of the invention is to provide an instrument of the kind hereinbefore alludedto, which may be made so cheaply that it can be sold for a small amount, "or be given away as an advertising novelty. A further object of the invention is to provide novel means for preventing a dislodgement of the needle or pendulum, and a downward swinging movement thereof, due to motions in the car not arising out of an application of thebrakes;

It is within the province of the disclosure to improve generally and to enhance the utility of devices of that type to which the present invention appertains.

With the above and other objects in view, which will appear as the description proceeds, the invention resides in the-combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed, may be made within the scope of what is claimed, without departing from the spirit of the invention.

In the accompanying drawing:

Fig. 1 shows in elevation, a device constructed in accordance with the invention;

Fig. 2 is a vertical section on the of Fig. i;

Fig. 3 is a top plan;

Fig. 4 is a top plan of the bracket and attendant parts, upon an enlarged scale.

In carrying out theinvention, ed a support I, in ,the form of a plate, having parallel inner and outer surfaces. The outer surface of the support I is placed against the inner surface of a pane 2 which, according to present practice, has vertical sliding adjustment in the side-front door of a motor car, the pane being located at the end of the drivers seat. The support I may be removably held on the pane 2 by any suitable means, for instance, by resilient clips 3 carried by the support and engaged over the upper edge of the pane.

A retainer 4 is secured to the support I and line 2-2 of has a head 5. A rotatable member 6 is mounted.

to turn for adjustment on the retainer 4, but the head 5 binds the rotatable member against the support I with suflicient friction so that the rotatable member will turn only if an operator scale reads oppositely to there is providbracket 8, within the notch 9.

October 14, 1936 Serial No. 105,591 (01. 264-1) applies sufficient force to a handle I which the rotatable member carries at its periphery. A bracket 8 is struck from theupper portion of the rotatable memberB and hasa circumfer- I entially extended notch 9. The rear end of the 5 notch 9 forms a seat III in the bracket. The inner edge I I of the notch 9 is parallel to the inner and outer surfaces of, the support I, but the outer edge I2 of the notch is disposed at an acute angle to the inner and outer surfaces of the support I, the notch 9 being slightly V-shaped, as Fig. 4 will show.

0n the lower portion of the rotatable member fi there is a scale I4. Since,-in a brake-testing machine, patentable novelty cannot be predi- 15 cated upon a specific basis for calibrating a scale, and since the scale may be constructed in various ways without departing from the spirit of the invention, the scale may be dismissed with the observation that it may be calibrated in any 20 way which will answer the end in view.

A pivot element I5 is carried by the retainer 4 and has a head It. A pendulum I1 is mounted on the pivot element I5, behind the head I6, for swinging movement in a plane parallel to the inner and outer surfaces of the support I, to wit, in the direction of the arrows A- and B in Fig. 1. The pendulum I'I also has swinging movement in a direction transverse to the inner and outer surfaces of the support I, as indicated-by the arrows 0 and D in Fig. 2.

The seat III of the stop bracket 8 and the zero of the scale I4 are in a straight line passing through the axis of the pivoteiement I5, and,- the vance of the car, that direction being indicated by the arrow E in Figs; .1 and 4. By way of further definition, it maybe stated that the notch 9 opens in the direction of advance of the car, namely in the direction of the arrow E, the scale 40 I4 reading in. an opposite direction.

Grossly considered, the operation is as follows:

The pendulum I1 is disposed in an upstanding, backwardly-inclined position, as in Fig; l the pendulum resting against the seat III of the The rotatable member 6 is turned by the handle I, in the direction of the arrow A, until the seat III and the upstanding pendulum II are close to a vertical line 2--2 passing through the axis of the pivot ele-' 5 ment I5, the seat and the upstanding pendulum being above the pivot element. The caris' put in motion, the brakes'are applied, and the pendulum II, responding to inertia, swings to a depending position and after the-vehicle is stopped,

the direction of the ad- 35 I position, the rotatable comes to rest opposite a graduation on the scale A reading on the scale is taken.

The pendulum II is restored to its upstanding member 6 is turned in the direction of the arrow B by steps of progressively-lessening amount, until the pendulum is not dislodged from the bracket 8 when the brakes are applied. The last reading taken on the scale I4, as indicated by the depending pendulum I'I, represents with suflicient accuracy, the maxi mum checking power of the brakes.

Taking up some of the finer points involved, the instrument, when a test is being made, will always be subjected to vibratory motions arising from road irregularities and the operation of the motor, and some of these motions acting in the plane of the member 6, will pendulum I1 downwardly, in the direction of the arrow A, from the lodged upstanding position of Fig. 1 to a depending position.

In practice, this tendency of the pendulum I1 1 to swing downwardly, due to vibratory or rapid oscillatory movements acting in the plane speci- 'fled, may, for all practical purposes, be disregarded, due to the presence of similar vibratory or oscillatory movements acting to the plane of the member 6, or in the direction of the arrows C and D of Fig. 2, and due to the particular shape of-the notch 9.

It can be seen in Fig. 4 that the notch 9 is elatively long and narrow. It is intended that the pendulum I! shall have a little loose motion in the notch 9, so that the pendulum may vibrate in the direction of the arrows C and D of Fig. 2, even when said pendulum rests. in the seat I 0. Thus it is apparent that when vibratory motions exist in the directions of the arrows C and D, the pendulum II will not travel straight out of the notch 9, as per arrow G of Fig. 4, for instance, even though inertial force might impel it to do so, but rather will be struck alternately by the edges I I and I2 of the notch 9, in rapid succession, and its forward movements thereby will be hindered.

This has been found to reduce the ill effects of vibratory movementsv formerly arising'in the course of a brake test to a negligible minimum.

A road jolt might give the pendulum II sufficient velocity in the direction of the arrow A to cause the pendulum to pass out of the notch '9 against the retarding effect of the component of gravity acting in the opposite direction, but the acceler ating force of said jolt ceases to act when the pendulum IT leaves the seat I 0, whereas the retarding effect of vibration in the direction of the arrows C and D continues to act, and thus bring the pendulum I1 to a halt before it has traveled far enough in G to materially affect the-performance of the instrument. n the other hand, an inertial force due to the application of the brakes, acting over a comparatively long period of time, a half second or more, if suflicient to overcome the coun-- teracting forces of gravityand friction at the pivot I6 will cause the pendulum. I1 to work its way, zigzag fashion, towards and out of the opening of the notch 9, after which it is free to swing rapidly'to a depending position.

The-foregoing being understood, it might be proposed that the edges II and ll of the notch 9 could be disposed in parallel relation, the pendulum I! being permitted to oscillate back and forth transversely of the support I, in the direction of the arrows dropping back by gravity against the seat I0.

tend to swing the at right angles the direction of the arrow.

C and D, the pendulum There is, however, another consideration to be carried in mind in determining the shape of the notch 9, so far as the angle between its edges II and I2 is concerned.

If the pane 2 of Fig. 1 were always disposed parallel to the arrow E in Fig. 4, representing the line of advance of the car, the support I would be correspondingly disposed, and a parallel-sidedv notch 9 might be employed. In many cars, however, the pane.2 is not disposed parallel to the line of advance of the car, but has a more or less pronounced forward and inward inclination, as indicated roughly by the arrow F in Fig. 4. If the pane 2 and the support I were inclined forwardly and'inwardly, as indicated roughly by the arrow F in Fig. 4, it wouldnot do to make the edge I2 of the notch 9 parallel to the edge II, because the edge I2 then would be interposed in front of the pendulum I1, and would tend to check the downward movement of the pendulum when the car brakes are applied. From what has been stated last above, itmay be ,assumed that to dispose the edge I2 of the notch at an acute angle to the edge II is desirable.

Assuming that, for the practical reasons above stated, the edge I2 of the notch 9 must be disposed at an acute angle to the edge II and at an acute angle to the inner and outer surfaces of the support I, it is to be noted that, as the pendulum II swings transversely in the direction of the arrows C and D in Fig. 2, a component in the direction of the arrow G in Fig. ,4, parallel to the edge I2, is resolved out of of the aforesaid transverse swinging movement, the component in the direction of the arrow G having a tendency to swing the pendulum I! out of the notch 9 and to permit the pendulum to drop to a depending position.

In order to avoid the contingency last' above described, care must be exercised in determining the inclination of the edge I2 of the notch 9. The angle defined by the edges II and I2 of the notch, (conveniently measured by the trigonometric tangent of said angle) must be such, considered relatively to the coeflicient of friction between the pendulum I1 and the bracket 8 along the edge I2, that when the pendulum oscillates transversely, as shown in Fig. 2 by the-arrows C and D, the component in the direction of the arrow G in Fig. 4 will not be sumciently great toovercome the friction between the pendulum I1 and the bracket 8 at the edge I2 of the notch. The end in view is, not to supply an instrument of precision, but to furnish 'a very simple article which will give satisfactory average result over a wide range, and answer the requirements of a motorist who wishes to know how his brakes are working, and the degree of their perfection within limits defined by such accuracy as the nature of a simple road test demands.

Having thus described the invention, what is claimed is:

I a device for testing the brakes of a .vehicle, a member carrying a pivot element, means for mounting said member on a vehicle in apabove the pivot element and to the rear of a vertical line passing through the pivot element, said member being provided with a rearwardly reading scale located below the pivot element, and a pendulum mounted atone end on the-pivot element for swinging movement in approximate parallelism to the line of advance of the vehicle, 4 the pendulum being of such length as to rest the scale, when the rest,

when

imately at right angles to the line oi advance of the vehicle, the stop being provided with a notch; one end of which receives the pendulum when the pendulum is in said rearwardly inclined position, one edge of the notch being inclined toward said member from the base of the notch to thegnouth or the notch,the inclination of said edge being such that when the pendulum oscillates in the last-specified direction, the'component forwardly along said edge will be offset by frictional contact between the pendulum and said edge, the pendulum then being left free to swing backwardly by gravity into contact with the stop at the base of the notch.

2. In a device for testing the brakes of a vehicle, a member carrying a pivot element, means for mounting said member on a vehicle in approximate parallelism to the lineoi advance of the vehicle, a. stop on said member and located above the pivot element and to the rear of a vertical line passing through the pivot element said member being provided with a rearwardlyreading scale located below the pivot element, and a. pendulum mounted at one end on the pivot the vehicle whereon the device element for oscillation mouth element for swln parallelism to the the pendulum beingof such length as to rest against the stop in an upstanding and rearwardly inclined position, the -inertia. or the; pendulum causing it to swing forwardly and out of engages ment with the stop, and downwardly into depending and indicating positionwlth respect to the scale; when the vehicle is subjected to braking eflort the pendulum when in said depending and indicating position the angular displacement of the stop only when r is mounted is at rest, the pendulum being mounted on the pivot in a direction'approximately at right angles to the line of advance of the vehicle,-the stop being provided with a notch, one end of which rejeives the pendulum when the pendulum is in s id rearwardly tion, one edge of the notch being inclined toward said member from the base of the notch to the of the notch, the inclination of said edge being such that when the pendulum oscillates in the last-specified direction, the component for wardly along said edge will be offset by a frictional contact between the pendulum and said edge, the pendulum then being left free to swing backwardly' by gravity into contact with the stop at the base of the notch, and means for mounting said member for rotation at the will of an operator andvior holding it against rotation otherwise,'the rotation of said member serving to adjust the stop toward and away iron said vertical line.

- PAUL WHITE CALHOUN.

g movement in approximatene of advance of the vehicle,.

giving an indication oi inclined p'osi- 

